39 The Church is a society, and as such requires an authority and hierarchy of her own. Though it is true that all the members of the Mystical Body partake of the same blessings and pursue the same objective, they do not all enjoy the same powers, nor are they all qualified to perform the same acts. The divine Redeemer has willed, as a matter of fact, that His Kingdom should be built and solidly supported, as it were, on a holy order, which resembles in some sort the heavenly hierarchy.
Source: Mediator Dei (Vatican.va)